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Re: [Xen-devel] RFC: Criteria for checking in core scheduling series
- To: George Dunlap <george.dunlap@xxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 6 Sep 2019 13:26:02 +0100
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- Cc: Juergen Gross <jgross@xxxxxxxx>, Lars Kurth <lars.kurth@xxxxxxxxxx>, Dario Faggioli <dario.faggioli@xxxxxxxxxx>
- Delivery-date: Fri, 06 Sep 2019 12:26:13 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 06/09/2019 12:09, George Dunlap wrote:
> There was a discussion on the community call about the core scheduling
> series being developed by Juergen Gross [1]. The conclusion can be
> summarized as follows:
>
> * We normally wait to check in series until they are quite good -- all
> the i's dotted and all the t's crossed
>
> * This is for several reasons; primarily because once code gets checked
> in, it rarely gets looked at again. In particular, there's nothing
> stopping the submitter from neglecting to do important clean-ups, in
> spite of their best intentions; leaving the maintainer or the rest of
> the community to do it.
>
> * However, for particularly long, complicated series like the core
> scheduling series, this can have significant downsides. Rebasing a
> 60-patch branch regularly is a lot of churn for little value; and core
> parts of the series which are mostly complete are currently only getting
> sporadic dev testing rather than the wide range of testing they would
> get from being in staging.
>
> * XenServer and SuSE are both long-term community members with a strong
> incentive to maintain and improve the feature; so the risk of the
> feature being left for the community to maintian is relatively now.
>
> With all those things in mind, the conclusion was to lower the
> "check-in" threshold from what it normally is, in order to allow the
> series to be checked in in the near future, in enough time at least for
> the "default off" to be well-tested by the 4.13 release.
>
> The criteria we sketched out were:
>
> * All the patches still need appropriate Ack / R-b's
>
> * There should be reason to believe that the series will have little to
> no impact on "thread mode" (threads being the unit of scheduling; i.e.,
> the status quo)
>
> WRT the second point, apparently XenServer have been testing the series
> regularly for some time, and are satisfied from a testing perspective
> that there is no significant degradation for the series when in "thread
> mode".
To clarify, we've been testing core mode, and providing feedback on the
xen-devel threads.
We are currently organising an extended regression test to run in thread
mode to increase the confidence of the previous bullet point.
> So this would really be a recommendation / license to the various
> maintainers involved; primarily Dario, I think (since I probably won't
> have time to review the series).
>
> No decisions are official until discussed on xen-devel; so the decision
> will not be considered official until a few days have passed without
> objection. And of course, if anyone at the meeting had a different
> understanding of what was said, or has something to add, please do so.
No objection from me at all.
~Andrew
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